Hi Tom,
I use Meld (and have used a few others). Haven't used it (or any of the
others) for LO or MS Office files, though.
It's pretty good for plain text files like config files or source code.
I've used it on generated files before (Visual Studio form files), and
it was helpful, but blocks of text that were the same tended to be
moved around arbitrarily, and showed up as differences in the file. I'm
not sure how much of a problem that would be with LO source files, but
in theory it should be helpful for determining if two copies of a file
are different, and by how much. That might allow you to determine which
version is more recent, that sort of thing.
Ideally I suppose one would want an LO viewer that allowed one to load
two files side-by-side, and scroll them in tandem. Maybe even have
differences, additions and deletions highlighted. A custom LO diff
tool, essentially. But short of that, something like Meld is probably
going to be useful.
Paul